[求助]請教TT GWD-4-16

Q16:

In the sequence of nonzero numbers t₁, t₂, t₃, …, t_n, …, t_n+1 = t_n / 2 for all positive integers n.  What is the value of t₅?

(1)       t₃ = 1/4

(2)       t₁ - t₅ = 15/16
                    

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

答案是D

我看不太懂= t_n / 2的意思

麻煩請NN幫忙啊

According t(n+1)=1/2 tn

so, t5=1/2 t4

t4=1/2 t3

t3=1/2 t2

t2=1/2 t1